PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Growth response of hardwood and conifer trees under different calcium nutrient regimes.
Edwards, Jenny1, Eissenstat, David1, 1 Pennsylvania State University, University Park, PA
ABSTRACT- Plant species differ in how they influence ecosystem structure and function including biogeochemical cycling, decomposition, pedogenesis and diversity and abundance of soil organisms. Differences among species in the acquisition of calcium and the cycling of calcium via leaf-litter may profoundly affect ecosystem processes. For example, evidence from a 30-year-old common garden planting of 14 species of conifer and hardwood trees in Poland indicates that species with high calcium in leaf litter have greater forest floor turnover rates, cation exchange capacity, base saturation, soil CO2 flux, and higher earthworm abundance. In this 16-week greenhouse study we examined six of these common garden species that vary in leaf Ca. We determined the calcium concentration at which optimal growth occurs, as well as the amount of calcium tree species were accumulating in their leaves. Species that differ in phylogeny were used, four conifers: Larix decidua, Pseudotsuga menziesii, Picea abies, and Pinus sylvestris and two hardwood species: Tilia cordata, and Betula pendula. These six species were grown in sand culture at three calcium levels (25 ppm, 2.5 ppm and 0.25 ppm) and at constant pH (5.0). The relative growth rate (RGR) was determined based on an 8-week sequential harvest. Tilia grew faster under high calcium than low calcium: RGR was 0.034 g g-1 day-1 in the high Ca treatment and 0.005 g g-1 day-1 in the low Ca treatment, whereas, the other species showed little growth rate response to different rates of Ca supply. However, at the end of the experiment, both Betula (32%) and Tilia (89%) had greater total biomass in the high Ca than the low. Concentration of leaf calcium after 12 weeks was measured. The data indicate the two hardwood tree species have stricter requirements for Ca nutrition than the conifer species and show more plasticity in Ca accumulation in their leaves.
Key words: calcium, nutrients, forests, trees